The present invention relates to a device for orienting magnetic particles distributed in a magnetic layer which constitutes a disc-shaped magnetic recording medium.
A magnetic recording medium is generally made up of a substrate, or support, made of nonmagnetic material and a magnetic layer or layers deposited on the substrate. For the fabrication of such a medium, it has been customary to move a magnetic recording medium through an orienting magnetic field while the magnetic layer is still wet, so that magnetic particles distributed in the magnetic layer may be oriented by the magnetic field. A magnetic tape, which is one typical form of magnetic recording media, is oriented in the longitudinal direction thereof, as well known in the art.
Another typical form of magnetic recording media is a disc available as a magnetic disc fabricated by applying magnetic layers to a substrate which is made of aluminum or like nonmagnetic metal, or a flexible disc, or floppy disc, fabricated by applying magnetic layers to a thin flexible substrate made of polyethylene terephthalate. In such a recording disc, tracks are provided in a format of concentric circles or in a spiral and, therefore, orienting the disc in the same manner as the tape, i.e. one straight direction, would limit the recording and playback sensitivity of the disc and, thereby, lower the playback output level or render it unstable. While an attempt has been made to produce a nonoriented magnetic recording disc in order to cope with the above problem, such a disc has naturally attained only poor recording and playback characteristics due to a low recording and playback sensitivity.
Orientation, therefore, is a requisite for magnetic discs as well as for magnetic tapes and it is highly desirable that magnetic particles are oriented along the circumference of a disc. In other words, the orientation at every radius of the disc is preferred to the tangential to the circumference of the disc. With prior art devices for orienting magnetic particles in a magnetic disc, there have remained difficulties in achieving accurate orientation of the magnetic particles in the circumferential direction of a disc.